Back up Flight Recorder for US contests

[Udo Rumpf]

I need help interpreting the 2006 rules regarding the above subject.
The rules do not discuss a back up flight recorder.
What options exist for a backup flight recorder that would be
excepted across the board in US contests for none team use.
Udo
PS. If you have a used GPS Nav 20 or 25 let me know.

[Charles Yeates]

Hi Udo

Is a backup needed? My GPS Nav has worked flawlessly for the last 10
years {:>))
>
> I need help interpreting the 2006 rules regarding the above subject.
> The rules do not discuss a back up flight recorder.
> What options exist for a backup flight recorder that would be excepted
> across the board in US contests for none team use.
> Udo
> PS. If you have a used GPS Nav 20 or 25 let me know.

--

[Udo Rumpf]

Hello Charles,
mine has worked flawlessly for many years as well.
I would like to have a second Nav / PDA system.
It should generates a flight log that is acceptable
as a back up for contests in the US.
If you like to know, I had a bit of a hick up in Florida with
my PDA I got it resolved in time but I wish, at that moment, I had
a second set-up. Having invested time and money for a contest
it could ruin an otherwise pleasant outing.
Udo

> Hi Udo
>
> Is a backup needed? My GPS Nav has worked flawlessly for the last 10
> years {:>))
>>
>> I need help interpreting the 2006 rules regarding the above subject.
>> The rules do not discuss a back up flight recorder.
>> What options exist for a backup flight recorder that would be excepted
>> across the board in US contests for none team use.
>> Udo
>> PS. If you have a used GPS Nav 20 or 25 let me know.
>
> --
>
>
>
>
>
>
>

[Marc Ramsey]

Udo Rumpf wrote:
>
> I need help interpreting the 2006 rules regarding the above subject.
> The rules do not discuss a back up flight recorder.
> What options exist for a backup flight recorder that would be excepted
> across the board in US contests for none team use.
> Udo
> PS. If you have a used GPS Nav 20 or 25 let me know.

You can use an off-the-shelf GPS unit (handheld, or track log capable
Bluetooth device) that records GPS altitude as a primary or backup
recorder, at any SSA sanctioned contest. You'll need to avoid cutting
the start altitude too close, to allow for the fact that GPS altitude
may be as much as 500 feet higher than indicated pressure altitude, due
to normal pressure altimetry errors.

Marc

[Papa3]

Udo,

I had the same issue as you and couldn't justify spending another
$800-$1000 for a "backup" (equal to one family vacation). So, I went
and bought a Garmin GPSMap76 for $130 on eBay. Best investment I ever
made! Advantages:

- Self-contained logger and display. So, no interface issues,
cables, software conflicts, etc.
- If you spend the time to get familiar with it, you can input a task,
set arrival radius, etc. It's easy to zoom in our out, and you can add
various maps to the background if you want to get fancy.
- Compact, so easy to mount. I molded a small cradle from plexiglas
and used the camera mounting holes provided in my LS8. RAM makes all
sorts of very slick mounts if you want something more elegant.
- It has been 100% reliable over the last year. In fact, it has been
so much easier to use when submitting OLC claims (given the recent VALI
issues) that it has been my primary logger for that purpose.
- As Marc cautions below, you need to be aware of the altitude
differences between barometric altitude and GPS altitude on anything
other than an ISA day. I have mine set up to show GPS Altitude on the
pointer screen itself; that way you have access to it in case you find
your Cambridge has gone down.
- You will need to have SeeYou, G72Win, or an equivalent program to
download and create an IGC format file.
- I use 2 rechargable 2500mAh rechargeable AA batteries which are good
for at least 6 hours each. I just swap 2 pairs each day during the
contest and I'm all set. I keep a spare pair of alkalines in the side
pouch just in case.

Hope this works for you.

Erik Mann (P3)

[Stewart Kissel]

You might check with Tom Stowers...he had one at High
Country Soaring for several years.

[Jack]

Papa3 wrote:

> I had the same issue as you and couldn't justify spending another
> $800-$1000 for a "backup" (equal to one family vacation). So, I went
> and bought a Garmin GPSMap76 for $130 on eBay. Best investment I ever
> made!

That works very well for me, too. Get the GPSMAP 76-S, with the
barometric sensor and compass. A few bucks more but better altitude
readings.


Advantages:
>
> - Self-contained logger and display. So, no interface issues,
> cables, software conflicts, etc.
> - If you spend the time to get familiar with it, you can input a task,
> set arrival radius, etc. It's easy to zoom in our out, and you can add
> various maps to the background if you want to get fancy.
> - Compact, so easy to mount. I molded a small cradle from plexiglas
> and used the camera mounting holes provided in my LS8. RAM makes all
> sorts of very slick mounts if you want something more elegant.
> - It has been 100% reliable over the last year. In fact, it has been
> so much easier to use when submitting OLC claims (given the recent VALI
> issues) that it has been my primary logger for that purpose.
> - As Marc cautions below, you need to be aware of the altitude
> differences between barometric altitude and GPS altitude on anything
> other than an ISA day. I have mine set up to show GPS Altitude on the
> pointer screen itself; that way you have access to it in case you find
> your Cambridge has gone down.
> - You will need to have SeeYou, G72Win, or an equivalent program to
> download and create an IGC format file.
> - I use 2 rechargable 2500mAh rechargeable AA batteries which are good
> for at least 6 hours each. I just swap 2 pairs each day during the
> contest and I'm all set. I keep a spare pair of alkalines in the side
> pouch just in case.
>
> Hope this works for you.
>
> Erik Mann (P3)
>

[Marc Ramsey]

Jack wrote:
> That works very well for me, too. Get the GPSMAP 76-S, with the
> barometric sensor and compass. A few bucks more but better altitude
> readings.

Careful, the pressure sensor equipped Garmins don't necessarily provide
"better" or "more accurate" altitude, at best, they provide "smoother"
altitude readings. Plus, if you get the calibration mode wrong, they
can give very poor results...

Marc

[Jack]

Marc Ramsey wrote:
> Jack wrote:
>> That works very well for me, too. Get the GPSMAP 76-S, with the
>> barometric sensor and compass. A few bucks more but better altitude
>> readings.
>
> Careful, the pressure sensor equipped Garmins don't necessarily provide
> "better" or "more accurate" altitude, at best, they provide "smoother"
> altitude readings. Plus, if you get the calibration mode wrong, they
> can give very poor results...

And how would we know which of the readings in the cockpit was more
accurate? We know better than to believe the altimeter on the panel when
it comes to consistent accuracy. I'll take GPS, properly calibrated to
barometric, if only because that's what goes in the file.

For OLC, why spend more?


Jack

[Marc Ramsey]

Jack wrote:
> Marc Ramsey wrote:
>> Careful, the pressure sensor equipped Garmins don't necessarily
>> provide "better" or "more accurate" altitude, at best, they provide
>> "smoother" altitude readings. Plus, if you get the calibration mode
>> wrong, they can give very poor results...
>
> And how would we know which of the readings in the cockpit was more
> accurate? We know better than to believe the altimeter on the panel when
> it comes to consistent accuracy. I'll take GPS, properly calibrated to
> barometric, if only because that's what goes in the file.

You have it backwards, it is barometric calibrated to GPS, if you have
it set up properly. Otherwise, it is just a slightly more inaccurate
than normal altimeter, with an arbitrary setting (unless you are, again,
very careful) and no calibration. And, there is no way to tell from the
track log or the IGC file what mode was actually used.

> For OLC, why spend more?

I'm actually suggesting spend less, go with the units that lack pressure
sensors, at least that way you (and the OLC) know exactly what you are
getting...

Marc

[Jack]

Marc Ramsey wrote:


> I'm actually suggesting spend less, go with the units that lack pressure
> sensors, at least that way you (and the OLC) know exactly what you are
> getting....

No argument -- 76, 76S, whatever does your job. Spend the money on tows.
As long as the IGC file is good, I'm happy.

But if I read you correctly you are saying that the altimeter in our
gliders are likely to be more accurate than GPS altitude throughout
their range. Is that your contention?


Jack

[Marc Ramsey]

Jack wrote:
> No argument -- 76, 76S, whatever does your job. Spend the money on tows.
> As long as the IGC file is good, I'm happy.
>
> But if I read you correctly you are saying that the altimeter in our
> gliders are likely to be more accurate than GPS altitude throughout
> their range. Is that your contention?

That is a different issue. GPS altitude and pressure altitude aren't
measuring the same thing. If you want to know your actual elevation
above the geode (or even "sea level"), GPS altitude, with all of its
fluctuations, will be far more accurate than any altimeter at anything
above a few thousand feet. If you want to know your pressure "altitude",
calibrated to a pressure gradient from an idealized model of the
atmosphere at a specific sea level temperature and pressure, then an ISA
calibrated barometric altimeter is the way to go.

The problem with the Garmin "S" models is that it is never clear exactly
what they are measuring. In auto-calibration mode, they use some sort
of long period (20 minutes or so) tracking algorithm to continuously
recalibrate the altimeter against GPS altitude. Works pretty well most
of the time, but I've seen the displayed altitude go off on a tangent at
times, for no apparent reason. In any other mode, it's not clear
whether they are using ISA or some other curve, whether there is any
temperature compensation, etc. So, either way, you end up with
something like "altitude" recorded, it's just never very clear exactly
what it is...

Marc

[Papa3]

Marc Ramsey wrote:
> > The problem with the Garmin "S" models is that it is never clear exactly
> what they are measuring. In auto-calibration mode, they use some sort
> of long period (20 minutes or so) tracking algorithm to continuously
> recalibrate the altimeter against GPS altitude. Works pretty well most
> of the time, but I've seen the displayed altitude go off on a tangent at
> times, for no apparent reason. In any other mode, it's not clear
> whether they are using ISA or some other curve, whether there is any
> temperature compensation, etc. So, either way, you end up with
> something like "altitude" recorded, it's just never very clear exactly
> what it is...
>
> Marc

I second Marc's point. I borrowed an S last year, and I also didn't
see any advantage; in fact, it was confusing. For post-flight
analysis, I'd much rather know that I'm using one standard (ie. WGS84)
rather than some hybrid standard (ie. pressure altitude kinda/sorta
adjusted to WGS84). The US contest rules (fairly) indicate that they
have to take the least favorable interpretation in terms of altitude,
and I wouldn't want there to be any debate about what was shown in the
log.

There are about 40 GPSMap76 units listed on eBay right now. If you
have some discipline, you should be able to get one for around $150.

P3

[Tim Mara]

Please look at my website "used" pages
http://www.wingsandwheels.com/page8.htm and
http://www.wingsandwheels.com/page20.htm
I typically have a used CAI loggers and sometimes other types taken on
trade.
tim
Wings & Wheels
www.wingsandwheels.com


"Udo Rumpf" > wrote in message
.. .
>
> I need help interpreting the 2006 rules regarding the above subject.
> The rules do not discuss a back up flight recorder.
> What options exist for a backup flight recorder that would be
> excepted across the board in US contests for none team use.
> Udo
> PS. If you have a used GPS Nav 20 or 25 let me know.